This invention is generally directed to toner and developer compositions, and more specifically the present invention is directed to toner compositions, including magnetic, single component, two component and colored toner compositions containing a wax component, In embodiments of the present invention, the toner is comprised of resin, especially a polyester resin, pigment, a wax component like polypropylene, or polyethylene, and the reaction product of an ethylene-glycidyl methacrylate copolymer with acid, or hydroxyl end groups, or mixtures thereof contained on the resin, which enables the grafted ethylene-glycidyl methacrylate copolymer to function as a compatibilizer and thus facilitate the dispersion of the wax as illustrated by the following ##STR1##
There is also provided in accordance with the present invention positively or negatively charged toner compositions comprised of polyester, pigment particles, a wax component, such as polypropylene wax, and a compatibilizer obtained by the reaction of the resin such as polyester acid end groups with an ethylene-glycidyl methacrylate copolymer, such as copolymers available from ELF Atochem North America Inc. as LOTADER.RTM. AX8840, believed to be a polyethylene-glycidyl methacrylate copolymer, thereby permitting substantial permanent dispersion of the wax, or minimizing the amount of wax released from the toner. Free wax particles associated with that of the toner can cause filming on a magnetic roll and adversely affect the function of a magnetic brush. In monocomponent development, wherein a charge/metering blade is used, the magnetic donor roll can be filmed by the wax and cause slipping of toner behind the metering blade thereby reducing the amount of toner on the donor roll for development. There also is the potential for filming of the photoreceptor by the free wax and, in those situations wherein magnetic brush cleaners are used, filming also can occur. Furthermore, free wax particles can coat the carrier particles causing a change in the tribocharging properties, thereby reducing developer life. Also, when toner has been prepared with wax and the wax is poorly dispersed so as to generate free wax particles upon attrition to toner size, the fines collected by classification are rich in wax and may not be recyclable because their composition is different and not well controlled. These and other disadvantages are avoided or minimized with the toners and processes of the present invention.
The toner and developer compositions of the present invention are useful in a number of known electrostatographic imaging and printing systems. The toner compositions of the present invention in embodiments possess a wide fusing latitude, for example about 40.degree. to 70.degree. C., which is the temperature range between the minimum fixing temperature of, for example, from about 100.degree. C. to about 180.degree. C. required for fixing toner particles on paper and the hot offset temperature, for example, from about 150.degree. C. to about 250.degree. C. Further, the toner compositions of the present invention also provide toner images with low surface energy and a low frictional coefficient, which properties enable the effective release of paper from the fuser roll and provide for a reduction in image smudging. Moreover, the developer compositions of the present invention possess stable electrical properties for extended time periods, and with these compositions, for example, there is no substantial change in the triboelectrical charging values.
Toners with waxes, such as polypropylene and polyethylene, are known. One problem associated with some of these toners, especially when the toner resin is a polyester, is that the wax component releases from the toner and adversely effects the toner characteristics, such as the toner triboelectric characteristics. For example, there are illustrated in U.K. Patent Publication 1,442,835, the disclosure of which is totally incorporated herein by reference, toner compositions containing resin particles and polyalkylene compounds, such as polyethylene and polypropylene, of a molecular weight of from about 1,500 to about 20,000, reference page 3, lines 97 to 119, which compositions prevent toner offsetting in electrostatic imaging processes. Additionally, the '835 publication discloses the addition of paraffin waxes together with, or without a metal salt of a fatty acid, reference page 2, lines 55 to 58. Also, in U.S. Pat. No. 4,997,739, there is illustrated a toner formulation including polypropylene wax with a M.sub.w of from about 200 to about 6,000 to improve hot offset. In addition, many patents disclose the use of metal salts of fatty acids for incorporation into toner compositions, such as U.S. Pat. No. 3,655,374. Also, it is known that the aforementioned toner compositions with metal salts of fatty acids can be selected for electrostatic imaging methods wherein blade cleaning of the photoreceptor is accomplished, reference U.S. Pat. No. 3,635,704, the disclosure of which is totally incorporated herein by reference. Additionally, there are illustrated in U.S. Pat. No. 3,983,045 three component developer compositions comprising toner particles, a friction reducing material, and a finely divided nonsmearable abrasive material, reference column 4, beginning at line 31. Examples of friction reducing materials include saturated or unsaturated, substituted or unsubstituted, fatty acids preferably of from 8 to 35 carbon atoms, or metal salts of such fatty acids; fatty alcohols corresponding to said acids; mono and polyhydric alcohol esters of said acids and corresponding amides; polyethylene glycols and methoxy-polyethylene glycols; terephthalic acids; and the like, reference column 7, lines 13 to 43.
The following U.S. Pat. Nos. are mentioned: 4,795,689 which discloses an electrostatic image developing toner comprising as essential constituents a nonlinear polymer, a low melting polymer, which is incompatible with the nonlinear polymer, a copolymer composed of a segment polymer, which is at least compatible with the nonlinear polymer, and a segment polymer, which is at least compatible with the low melting polymer, and a coloring agent, see the Abstract, and columns 3 to 10 for example; 4,557,991 which discloses a toner for the development of electrostatic images comprised of a certain binder resin, and a wax comprising a polyolefin, see the Abstract; also, see columns 5 and 6 of this patent and note the disclosure that the modified component shows an affinity to the binder and is high in compatibility with the binder, column 6, line 25; and as collateral interest 3,965,021.
Described in U.S. Pat. No. 4,367,275 are methods of preventing offsetting of electrostatic images of the toner composition to the fuser roll, which toner subsequently offsets to supporting substrates, such as papers, wherein there are selected toner compositions containing specific external lubricants including various waxes, see column 5, lines 32 to 45.
However, there are various problems observed with the inclusion of polyolefins or waxes in toners. For example, when a polypropylene wax is included in a toner to enhance the release thereof from a hot fuser roll, or to improve the lubrication of a fixed toner image, it has been observed that the wax does not disperse well in the toner resin. As a result, free wax particles are released during the pulverizing step in, for example, a fluid energy mill. The poor dispersion of wax in the toner resin and, therefore, the loss of wax will then impair the release function it was designed for. Scratch marks, for example, on xerographic developed toner solid areas caused by stripper fingers have been observed as a result of the poor release. Furthermore, the free wax remaining in the developer can build up on the detone roll present in the xerographic apparatus causing a hardware failure.
All the problems mentioned above and others can be eliminated, or minimized with the toner compositions and processes of the present invention in embodiments thereof. The release of wax particles is, for example, a result of poor wax dispersion during the toner mechanical blending step. The toner additives should be well dispersed in the primary toner resin for them to impart their specific functions to the toner and thus the developer. For some of the additives, such as waxes like polypropylene, VISCOL 550P.TM. that become a separate molten phase during melt mixing, the difference in viscosity between the wax and the resin can be orders of magnitude apart, thus causing difficulty in reducing the wax phase domain size. Also, poor dispersion can be caused by the inherent thermodynamic incompatibility between polymers. The FIory-Huggins interaction parameter between the resin and the wax is usually positive (repulsive) and large thus interfacial energy remains very large in favor of phase separation into large domains to reduce interfacial area. Some degree of success has been obtained with regard to reducing free wax by mechanical blending the toner formulation in certain types of mixers, such as the known Banbury mixer and rubber mills, where the temperature of melt can be maintained at a low level and polymer viscosities are not that far apart, however, it is difficult to generate an effective wax dispersion in compounding extruders where melt temperatures are typically higher. Inclusion of the compatibilizer of the present invention is designed to overcome the inherent incompatibility between different polymers, and, more specifically, between toner resin and wax, thus widening the processing temperature latitude and enabling the toner preparation in a large variety of equipment, for example an extruder. Also, with the present invention the improvement in thermodynamic compatibility will provide for a more stable dispersion of secondary polymer phase, such as wax, in the host resin against gross phase separation over time.
Illustrated in U.S. Pat. No. 5,229,242 (D/91096), the disclosure of which is totally incorporated herein by reference, is a toner composition comprised of resin particles, pigment particles, wax component particles, and a compatibilizer; a toner composition comprised of first resin particles, second crosslinked resin particles, pigment, wax component particles, and a compatibilizer comprised of a graft copolymer, or a block copolymer; and a toner composition in accordance with claim 2 wherein the compatibilizer is of the formula A-b-B, A-b-B-b-A or A-g-B wherein A-b-B is a block copolymer of 2 segments; A and B, A-b-B-b-A is a block copolymer of 3 segments; and A-g-B is a graft copolymer of segments A and B.
In the present invention, the compatibilizing agent ethyleneglycidyl ester is reacted with the resin like a polyester and as such, will not interfere with the toner functionality, such as in fusing, wherein it is known that certain waxes with functional groups, for example oxidized waxes, can have an affinity for the fuser roll surface, coat surface thereof and shorten fuser life. In those situations wherein a block polymer is used as a compatibilizer, ideally, each segment needs to be specifically designed to be compatible with each phase for optimal performance. This may not always be feasible, particularly when a relatively low molecular weight polyester is the binder resin. In the present invention, the glycidyl ester reacts with the polyester end groups thereby grafting polyethylene onto the polyester, and one then need only be concerned with the polyethylene to compatibilize the wax.
A number of specific advantages are associated with the invention of the present application in embodiments thereof, including improving the dispersion of toner resin particles, especially a mixture of resins and wax; improving the dispersion of wax in the toner, thus eliminating the undesirable release of wax from the toner in the form of free wax particles during the pulverizing operation of the toner manufacturing process and the subsequent contamination of xerographic machine subsystems by these free wax particles; maintaining the intended concentration of wax in the toner to provide enhancement during release from the fuser roll and avoiding the undesirable scratch marks caused by the stripper fingers; a wide process latitude can be provided during the mechanical blending operation of the toner manufacturing process; enabling the effective mechanical blending of toner to be accomplished in a number of devices, including an extruder; prevention, or minimization of toner component interactions with charge additives, pigments, the fuser roll, improved toner and developer powder flow characteristics, and the like.